A problem I always experienced with Invision is it loosing ALL the saved settings whenever, for any reason, you quickly disconnect a reconnect to a server.
This is VERY FRUSTATING since you have to spend 20 minutes re-configuring everything. Even the presets (encrypt key, nick tag) go away.
IMO this is the worst problem in Invision and should be on the top of the TODO list. There are other scripts that lack many cool features Invision has, but are robust in keeping the settings.